Arterial and venular endothelial cell costimulation of cytokine secretion by human T cell clones

Cardiovascular disease complications in systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is a highly variable autoimmune disease characterized by aberrant host-immune responses and chronic inflammation. Recently, a strong association between cardiovascular (CV) disease and SLE has emerged. Thus, low serum, high-density lipoprotein strongly correlated with elevated erythrocyte sedimentation rate, IL-6, TNF-alpha and the SLE disease activity index after adjusting for age, gender, race, BMI, insulin sensitivity and any concurrent drug use. In SLE, CV disease is characterized by increased VEGF, which may alter vascular hemostasis and promote neoangiogenesis. Increased low-density lipoprotein-cholesterol and proinflammatory high-density lipoprotein-cholesterol uptake by monocytes together with enhanced low-density lipoprotein-cholesterol oxidation results in the deposition of altered cholesterol forms into the vascular wall. This contributes to precocious and accelerated development of coronary artery plaques. Cholesterol-reducing drugs should be considered in the standard of care of SLE patients, especially in those with an unfavorable CV disease risk profile, which could reduce the probability of atherosclerosis progressing to CV disease or stroke in these patients.

Modulation of human T cells signaling transduction by lovastatin

Statins are applied clinically to treat hypercholesterolemia and proposed to have some kinds of anti-inflammatory properties for reducing the incidence of atherosclerosis-related cardiovascular events. However, it was rarely known about statins on the signal transduction on human primary T cells. To gain insight into the mechanism of statins on human T cells, we investigated the effects of both lovastatin and atorvastatin on activated human primary T cells. The human primary T cells from the blood of normal human beings were isolated. We found that lovastatin, but not atorvastatin, can dose-dependently inhibit cytokine production such as interleukin-2, interleukin-4, and interferon-gamma from activated human T cells. Neither lovastatin nor atorvastatin can regulate the TNF-alpha production on both activated human T cells and monocytes. Molecular investigation was performed that lovastatin, but not atorvastatin, could down-regulate both activator protein-1 and NF-kappaB DNA binding activities, assessed by electrophoretic mobility shift assay. Our observations may extend potential and differential therapeutic mechanisms of lovastatin with cell-mediated capacity to prevent or treat some of inflammation related diseases.

Statins and the endothelium

Statins have been shown to have pleiotropic effects apart from serum lipid-lowering effect in human. One of the major target organs for the effects of statins is the vascular endothelium, which plays an important role in the development of atherosclerosis and angiogenesis. Recent numerous studies have shown that the statins' cholesterol-independent vascular effects appear to involve directly restoring or improving endothelial function by increasing NO production, promoting re-endothelialization after arterial injury, and inhibiting inflammatory responses within the vessel wall that are thought to contribute to atherosclerosis. This review provides an update of the unique effects of statins on endothelial cells including endothelial progenitor cells as well as highlighting the therapeutic potential of statins beyond their established lipid-lowering effects.

Sustained delivery of bioactive cytokine using a dense collagen gel vehicle

OBJECTIVE

The use of cytokines as localized therapeutic agents is limited by the lack of a satisfactory delivery system. The aim of the current investigation was to determine the release kinetics and bioactivity of a simplified cytokine/collagen gel system designed to achieve extended, local delivery of bioactive cytokines at sites of premature cranial suture fusion (craniosynostosis).

DESIGN

Cytokine release was determined by ELISA measurements of Tgf-beta3 collected in media. Cytokine bioactivity was determined by measuring the effect of conditioned media, containing released Tgf-beta3, on mink lung epithelial cell proliferation and osteoblast alkaline phosphatase activity. Osteoblast response was evaluated by measuring proliferation of cells cultured on collagen gel containing Tgf-beta3 using an AlamarBlue assay.

RESULTS

Gels loaded with 100 and 500 ng of Tgf-beta3 produced a sustained release over 14 days with a pattern of initial large release followed by a gradual reduction in the amount released over the time. The reduced release over time was correlated to the amount initially loaded. Mink lung epithelial cell assay results indicated that Tgf-beta3 released from the collagen gel retained its bioactivity following incorporation into the collagen gel and release into the media. This bioactivity was further illustrated by a decreased alkaline phosphatase activity measured in osteoblasts cultured on the gels loaded with Tgf-beta3. Osteoblast proliferation assays demonstrated that the collagen gel has an inherent inhibitory effect on osteoblast cell number.

CONCLUSIONS

This collagen gel/cytokine delivery system can retain and release bioactive cytokine over a prolonged period. These results will allow for better optimization of future in vitro and in vivo studies directed at improving the treatment of craniosynostosis.

Cross-presentation of oral antigens by liver sinusoidal endothelial cells leads to CD8 T cell tolerance

After ingestion, oral antigens distribute systemically and provoke T cell stimulation outside the gastrointestinal tract. Within the liver, scavenger liver sinusoidal endothelial cells (LSEC) eliminate blood-borne antigens and induce T cell tolerance. Here we investigated whether LSEC contribute to oral tolerance. Oral antigens were efficiently cross-presented on H-2K(b) by LSEC to naive CD8 T cells. Cross-presentation efficiency in LSEC but not dendritic cells was increased by antigen-exposure to heat or low pH. Mechanistically, cross-presentation in LSEC requires endosomal maturation, involves hsc73 and proteasomal degradation. H-2K(b)-restricted cross-presentation of oral antigens by LSEC in vivo induced CD8 T cell priming and led to development of CD8 T cell tolerance in two independent experimental systems. Adoptive transfer of LSEC from mice fed with antigen (ovalbumin) into RAG2-/- knockout mice, previously reconstituted with naive ovalbumin-specific CD8 T cells, prevented development of specific cytotoxicity and expression of IFN-gamma in CD8 T cells. Using a new transgenic mouse line expressing H-2K(b) only on endothelial cells, we have demonstrated that oral antigen administration leads to tolerance in H-2K(b)-restricted CD8 T cells. Collectively, our data demonstrate a participation of the liver, in particular scavenger LSEC, in development of CD8 T cell tolerance towards oral antigens.

Human endothelial cells enhance human immunodeficiency virus type 1 replication in CD4+ T cells in a Nef-dependent manner in vitro and in vivo

Infected CD4+ T cells are the primary sites of human immunodeficiency virus type 1 (HIV-1) replication in vivo. However, signals from professional antigen-presenting cells (APCs), such as dendritic cells and macrophages, greatly enhance HIV-1 replication in T cells. Here, we report that in cocultures, vascular endothelial cells (ECs), which in humans can also serve as APCs, can enhance HIV-1 production of both CCR5- and CXCR4-utilizing strains approximately 50,000-fold. The observed HIV-1 replication enhancement conferred by ECs occurred only in memory CD4+ T cells, required expression of major histocompatibility complex class II (MHC-II) molecules by the ECs, and could not be conferred by fixed ECs, all of which are consistent with a requirement for EC-mediated T-cell activation via T-cell receptor (TCR) signaling. Deletion of nef (Nef-) decreased HIV-1 production by approximately 100-fold in T cells cocultured with ECs but had no effect on virus production in T cells cocultured with professional APCs or fibroblasts induced to express MHC-II. Human ECs do not express B7 costimulators, but Nef- replication in CD4(+)-T-cell and EC cocultures could not be rescued by anti-CD28 antibody. ECs act in trans to enhance wild-type but not Nef- replication and facilitate enhanced wild-type replication in naive T cells when added to T-cell or B-lymphoblastoid cell cocultures, suggesting that ECs also provide a TCR-independent signal to infected T cells. Consistent with these in vitro observations, wild-type HIV-1 replicated 30- to 50-fold more than Nef- in human T cells infiltrating allogeneic human skin grafts on human huPBL-SCID/bg mice, an in vivo model of T-cell activation by ECs. Our studies suggest that ECs, which line the entire cardiovascular system and are, per force, in frequent contact with memory CD4+ T cells, provide signals to HIV-1-infected CD4+ T cells to greatly enhance HIV-1 production in a Nef-dependent manner, a mechanism that could contribute to the development of AIDS.

T lymphocyte-endothelial cell interactions

Human vascular endothelial cells (EC) basally display class I and II MHC-peptide complexes on their surface and come in regular contact with circulating T cells. We propose that EC present microbial antigens to memory T cells as a mechanism of immune surveillance. Activated T cells, in turn, provide both soluble and contact-dependent signals to modulate normal EC functions, including formation and remodeling of blood vessels, regulation of blood flow, regulation of blood fluidity, maintenance of permselectivity, recruitment of inflammatory leukocytes, and antigen presentation leading to activation of T cells. T cell interactions with vascular EC are thus bidirectional and link the immune and circulatory systems.

Endothelial cells present antigens in vivo

Background

Immune recognition of vascular endothelial cells (EC) has been implicated in allograft rejection, protection against pathogens, and lymphocyte recruitment. However, EC pervade nearly all tissues and predominate in none, complicating any direct test of immune recognition. Here, we examined antigen presentation by EC in vivo by testing immune responses against E. coli β-galactosidase (β-gal) in two lines of transgenic mice that express β-gal exclusively in their EC. TIE2-lacZ mice express β-gal in all EC and VWF-lacZ mice express β-gal in heart and brain microvascular EC.

Results

Transgenic and congenic wild type FVB mice immunized with β-gal expression vector DNA or β-gal protein generated high titer, high affinity antisera containing comparable levels of antigen-specific IgG1 and IgG2a isotypes, suggesting equivalent activation of T helper cell subsets. The immunized transgenic mice remained healthy, their EC continued to express β-gal, and their blood vessels showed no histological abnormalities. In response to β-gal in vitro, CD4⁺ and CD8⁺ T cells from immunized transgenic and FVB mice proliferated, expressed CD25, and secreted IFN-γ. Infection with recombinant vaccinia virus encoding β-gal raised equivalent responses in transgenic and FVB mice. Hearts transplanted from transgenic mice into FVB mice continued to beat and the graft EC continued to express β-gal. These results suggested immunological ignorance of the transgene encoded EC protein. However, skin transplanted from TIE2-lacZ onto FVB mice lost β-gal⁺ EC and the hosts developed β-gal-specific antisera, demonstrating activation of host immune effector mechanisms. In contrast, skin grafted from TIE2-lacZ onto VWF-lacZ mice retained β-gal⁺ EC and no antisera developed, suggesting a tolerant host immune system.

Conclusion

Resting, β-gal⁺ EC in transgenic mice tolerize specific lymphocytes that would otherwise respond against β-gal expressed by EC within transplanted skin. We conclude that EC effectively present intracellular "self" proteins to the immune system. However, antigen presentation by EC does not delete or anergize a large population of specific lymphocytes that respond to the same protein following conventional immunization with protein or expression vector DNA. These results clearly demonstrate striking context sensitivity in the immune recognition of EC, a subtlety that must be better understood in order to treat immune diseases and complications involving the vasculature.

Delivery of transforming growth factor-beta2-perturbing antibody in a collagen vehicle inhibits cranial suture fusion in calvarial organ culture

OBJECTIVE

To determine whether antibody perturbation of Tgf-beta, delivered in a collagen gel, could inhibit cranial suture fusion.

DESIGN

Attachment and proliferation of osteoblasts cultured on a collagen gel with or without anti-Tgf-beta2 antibody were determined by AlamarBlue dye assay and cell morphology by toluidine-blue staining. In rat calvarial organ culture, collagen gel with and without anti-Tgf-beta2 antibody was injected subperiosteally over the posterior frontal suture of postnatal day 15 rat calvariae. A quantitative analysis of suture fusion was used to measure suture bridging in histological serial sections at various time points.

RESULTS

Attachment and proliferation for cells cultured on collagen gel with anti-Tgf-beta2 antibody were similar to collagen gel controls. Although proliferation was lower than on tissue culture plastic, cells treated with anti-Tgf-beta2 antibody maintained an osteoblastic morphology. After 7, 10, and 15 days in organ culture, anti-Tgf-beta2 antibody treatment caused a reduction in the percent bridging of posterior frontal sutures, compared with controls. Sutures exposed to anti-Tgf-beta2 antibody and fibroblast growth factor-2 concurrently did not show an inhibition of bony bridging.

CONCLUSIONS

These results support previous reports suggesting a role for Tgf-beta2 in cranial suture fusion. In cell culture the collagen gel, both with and without anti-Tgf-beta2 antibody, promoted similar osteoblast attachment, proliferation, and osteoblastic morphology. In organ culture anti-Tgf-beta2 antibody was delivered in a bioactive state via a collagen gel to inhibit cranial suture fusion. Also, the results suggest that the inductive effect of fibroblast growth factor-2 is not dependent on Tgf-beta2 activity. Together, these results provide further support for the role of Tgf-beta2 in cranial suture fusion.

Fibroblast growth factor 2 induces increased calvarial osteoblast proliferation and cranial suture fusion

OBJECTIVE

Craniosynostosis has been associated with fibroblast growth factors (FGFs) and their receptors. The purpose of this study was to quantitatively determine the effect of FGF2 on rat calvarial osteoblasts and a rat cranial suture formation model.

DESIGN

Fetal rat calvarial osteoblasts were cultured with and without FGF2. Cell attachment and proliferation was determined by alamar Blue dye assay and cell morphology by toluidine-blue staining. In rat calvarial organ culture, postnatal day 15 rat calvariae with dura mater were placed in serum-free media with and without FGF2. A unique quantitative analysis of suture fusion was developed by obtaining measurements of suture bridging in histological serial sections at progressive stages of fusion.

RESULTS

Attachment for cells treated with FGF2 was similar to control. In contrast, proliferation was higher for cells treated with FGF2 while maintaining an osteoblastic morphology. After 5 days in organ culture, FGF2-treated posterior frontal sutures showed a dramatic increase in fusion, compared with untreated controls. This increased fusion was maintained throughout days 7 and 10 in culture. Also, fusion was enhanced on the dural side of the suture, as is normally observed in vivo, and the normal tissue architecture was maintained.

CONCLUSIONS

These results indicate that FGF2 can promote rat osteoblast attachment and normal cell morphology as well as induce cell proliferation. In calvarial organ culture, FGF2 treatment produced an enhanced suture fusion. These results provide further support for a critical role for FGF2 in cranial suture development. These studies also present a new quantitative approach to evaluating the effect of suture-perturbing growth factors on cranial suture fusion.

Immunopathogenesis of vasculitis

Vasculitis is defined by the presence of leukocytes in the vessel wall with reactive damage to mural structures, leading to tissue ischemia and necrosis. The immunopathologic events that initiate the process of vascular inflammation and blood vessel damage are unclear. Damage of vascular endothelial cells and the recruitment and accumulation of the inflammatory infiltrate are determined by the endothelial cell and the bystanders, including the expression of adhesion molecules, the secretion of peptides and hormones, and the specific interaction with inflammatory cells. In addition to the endothelial cells, which provide costimulatory function, other cellular components and nonendothelial structures of the vessel wall are involved in controlling the inflammatory process, serve as antigen-presenting cells, and contribute with inflammatory mediators.